Pneumatic pumping devices using pump cassettes are known in the art. Among other things, pump cassettes typically include various membrane-based chambers and valves that are pneumatically actuated by a control assembly. During use, the control assembly is aligned and pressed in very close face-to-face contact against the pump cassette. Such alignment and contact permit the control assembly to precisely actuate the cassette chambers and valves, thus regulating fluid flow through the cassette. Precise actuation permits the overall pumping device to pump precise amounts of fluid.
To those ends, the control assembly typically includes a front surface that is sealingly pressed against a rear surface of the pump cassette. The front surface of the control assembly includes membranes that align with chambers and valves in the cassette. The membranes in the control assembly are pneumatically controlled to inflate and deflate in a manner that precisely controls operation of corresponding valves and chambers in the cassette.
During operation, it is important to ensure appropriate sealing alignment and close face-to-face contact between the cassette and control assembly. Improper spacing, sealing, or alignment between the control assembly and cassette undesirably can impact the precision with which the cassette chambers are expanded and contracted. Consequently, the fluid amounts pumped by the cassette can be inaccurate.